Electrical motors for hermetical-sealing applications require a feed-through unit which directs electrical energy from the surroundings into the interior of a hermetically sealed motor housing. The feed-through unit must in this regard be sealed gas-tight in connection with the motor housing.
Various electrical feed-through units for hermetic sealing purposes are known. In DE 10 2010 043 773 B4, an electrical feed-through unit for hermetically-sealed compressors in refrigerant cycles is disclosed. The attachment pin and the elastic insulation material are under tension and lead through an opening of the housing of the hermetically-sealed compressor. The attachment pin and the insulating material are connected with each other by vulcanized joining.
In DE 33 24 466 A1, an electrical feed-through unit is disclosed for electric motors. Here, buds made of an insulating and elastic material admit the guiding pin. A bead made of insulating and elastic material provides resistance against the feed-through unit being pressed out of the housing.
DE 10 2006 041 940 A1 discloses an electrical feed-through unit for use in electrical therapy devices such as cardiac pacemakers. The electrical feed-through unit is hermetically sealed off by means of a filler. Here the filler is glass or glass ceramic, which ensures electrical insulation of the feed-through unit.
DE 39 09 186 A1 discloses another electrical feed-through unit for hermetical sealing applications. With this, an attachment line is secured in an active filler sheath, which is soldered in a borehole of the housing.
In practice, electrical feed-through units made of GTMS (glass-to-metal feed-through) are widely made use of. These consist of an outer steel body in which one or more glass bodies are smelted. A glass body, in turn, comprises the actual metallic, thus electrically conducting, pins, and the glass part electrically insulates the pin from the outer steel body.
The GTMS is attached on the motor housing, and requires either a separate seal and attachment material, or it is compressed into the motor housing, with the outer surface of the steel body forming a metallic seal with the motor housing. The arrangement is secured in the motor housing against becoming loose by, for example, a clip, and is hermetically sealed by an O ring, thus a ring-shaped sealing element. As a rule, the GTMS is incorporated before stator installation.
From a functional standpoint, i.e. as regards structural space, pressure impingement and pressure direction, it is desirable to install the stator and electrical feed-through unit into the motor housing in the same fitting direction. If the stator is already installed in the motor housing, only a limited freely-accessible area remains for installing the GTMS. In the case of an interior runner this is within the interior diameter of the stator, and in the case of an exterior runner, outside the stator exterior diameter.
However, as a rule, the GTMS requires more space for assembly. For this reason, electrical feed-through units are often placed outside the motor diameter, which requires additional room for the application and increases the overall structural space of the engine housing.
Alternatively, the assembly sequence can be changed, in that first the GTMS is attached in the housing, and then the stator is inserted. Then the feed-through unit lies behind the stator and no longer is freely accessible. This results in a difficult assembly operation or in a blind operations when the stator winding then makes contact with the GTMS.
A further disadvantage of the known GTMS are the large apertures required in the housing, which contribute to a weakening of the overall structure, which is especially relevant in high-pressure applications such as a carbon dioxide compressor.
Additionally, the difficult GTMS manufacturing process results in higher tolerances of electrically conducting pins. Along with that, the manufacturing process and also the later application places limits on choices for material of the current-carrying line to steel, which does not have good electrical properties. Lastly, due to brittleness of glass, GTMS is very sensitive to mechanical effects such as shear forces or torsion, which may appear during the assembly process.
The object of the invention is to provide an electrical motor that is particularly suited for hermetically-sealing, thus gas-tight, applications, and can from outside be supplied with the required electrical energy. An effort is also made to produce the electrical feed-through unit and to further install it in a more cost-efficient manner, and to make the feed-through unit design more flexible in positioning.